The author sheds light on the varieties of darkness that shade the life and thought of, arguably, Germany's most influential 20th-century philosopher. Safranski (Schopenhauer and the Wild Years of Philosophy, not reviewed) presents Heidegger in the context of what Osers, the book's translator, so brilliantly calls ``that German specialty for extravagant wretchedness.'' More than most German philosophers, Heidegger, in quest of Being, pushes to the brink of incomprehensibility. The author comforts us with the knowledge that even so distinguished a friend of Heidegger's as Karl Jaspers, missed what Heidegger meant by ``Being.'' But the darkness of incomprehension was itself a principle of Heidegger's thought. Instead of the active, determining mind that Kant had posited, Heidegger found an intractable resistance to human reason--Being itself--of which we first become aware in amazement over the sheer fact that anything exists at all. We do not so much shape the world as find ourselves ``being there,'' or in German, Dasein. Against this cognitive darkness, Safranski sets the moral obscurity of Heidegger's Nazi involvement and tries to unravel the connections there between the philosopher's thought and life. The picture that emerges is, appropriately, darkly unfocused. When Safranski observes at the end of his book that Heidegger's ``brusqueness and severity'' mellowed with age, readers will wonder whether they've missed something: Brusqueness is already too defined a quality for what Hannah Arendt called Heidegger's ``lack of character, in the sense that he literally has none, certainly not a particularly bad one.'' Safranski suggests that the real Heidegger hovers between two self-portraits: modern tower of philosophy and modest attendant in the museum of philosophy's history, taking care that the works on display there are properly illuminated. Safranski's own take--both critical and appreciative--on Heidegger mirrors the complexity of his subject, and provides a welcome entrÇe to a difficult thought world.